This invention relates to a transit mixer, and more particularly to a contractible-extendable trailer transit mixer adapted to discharge forwardly of the truck.
The necessity for moving large quantities of building material such as concrete for long distances has resulted in various styled trucks designed to address particular load and terrain requirements. These truck designs were of two basic types. First, and most popular, the mixer drum was mounted on the truck body thereby providing acceptable manueverability of the vehicle. Second, the mixer drum was mounted on a trailer portion which was then secured to the truck body. This particular trailer configuration resulted in greater pay load capability due to better axel load characteristics but sacrificed maneuverability.
Illustrative of the previous forms of trailer transit mixers characterized by a configuration having a trailer to which a mixer drum assembly was mounted to hold the pay load during transit is U.S. Pat. No. 3,038,704. A separate engine or other drive mechanism integral with the truck body was connected to the mixer drum to cause rotation and provide the desired mixing necessary during the transportation or discharge of concrete. The mixer drum was positioned on the trailer with the open end at either the front or rear with discharge chutes mounted at the open end to discharge concrete at the front or rear of the trailer depending upon the operational characteristics desired.
In the configuration of U.S. Pat. No. 3,038,704, the drum was rotatably mounted to point forward on a trialer portion which was slidably engaged with the truck body. However, this form had severely impaired turning capabilities when in the contracted configuration due to the contracted trailer portion extending along side the truck cab.
Other trailer type devices have been used with transit mixers to increase the payload carried by the mixer drum, such as those of U.S. Pat. Nos. 3,019,022 and 3,112,100, but these prior art trailer devices had various limitations and undesirable operational characteristics.
Additionally, due to the highway regulations of the Federal Government, all states and many foreign governments, there are severe restricts on the size and loading of trucks and trailers that use public roads. In particular, various limitations exist directed to the weight per axle per unit length of trucks or trailers allowable on public highway facilities. For example, California highway regulations require total vehicle weight to be less than 80,000 lbs, for vehicles having 5 axles and of a length less than 51 feet between the extreme spaced axles. For vehicles having 4 axles the spacing between the extreme axles must be at least 57 feet to carry 80,000 lbs. The Federal Government and many states place a limitation of 80,000 lbs. on total vehicle weight when loaded regardless of the number of axles.
Therefore, by simply making the transit mixer drum larger, thereby increasing the payload and weight but without increasing the length, the manufacturer and user may face violations of Federal or State Codes. Similarly, by making the transit mixers longer, as illustrated by multiaxle trailers, manueverability problems exist at the job site. Also, in the longer trailer transit mixer configurations insufficient drive wheel traction can occur at the job site, thus reducing the ability of the trailer transit mixer to negotiate adverse terrain. There are still further State and Federal highway regulations that limit the total weight allowable on a single axle or on tandem axle configurations.